1. Field of the Invention
The present invention relates to a display apparatus for a vehicle in which light emitted by a light source passes through a slit so as to be used as a luminous pointer.
2. Description of the Prior Art
A self-light-emitting type display apparatus with a disk-shaped pointer having a linear light-transmissible portion, which is rotated by an instrument unit, has been used to display information on driving conditions such as vehicle speed for a driver. In this conventional display apparatus, a linear light passes through the light-transmissible portion is used as a luminous pointer.
FIGS. 16 to 19 show the conventional display apparatus for a vehicle with the above construction. A substantially circular light-diffusing portion 2 is formed on a dial 1 made of a light-diffusing plate, which is disposed in an instrument case mounted on a dashboard of a vehicle. Light-transmissible characters 3a and graduations 3b are situated on an outer periphery of the light-diffusing portion 2. A light-intercepting layer 4 with black color or the like is formed on a surface of a portion excluding the light-diffusing portion 2, the characters 3a and the graduations 3b. A center hole 5 is formed in the middle of the light-diffusing portion 2 through which a rotating shaft of an instrument movement 6 with cross-coil type or the like passes.
A disk-shaped pointer plate 8 is positioned on the front side of the dial 1. The pointer plate 8 is made of transparent material such as an acrylics or polycarbonate, and has a slightly large diameter than that of the light-diffusing portion 2. A rotating shaft 7 is connected and fixed to the pointer plate 8. Further, a light-transmissible slit 9 as a pointer radially extends from the center of the pointer plate 8 to an end thereof. The light-intercepting layer 4 is formed on a surface of a portion of the pointer plate 8 except for an area of the slit 9. A ring-shaped cathode ray tube 10 as a light source is situated on the rear side of the pointer plate 1 in such a manner as to enclose the instrument movement 6.
In the conventional display apparatus described above, on switching on the cathode ray tube 10, the light emitted by the light source 10 is irradiated on a rear face of the dial 1 and passes the light-diffusing portion 2 to reach the rear face of the pointer plate 8. Then, the light from the light source passes through portions corresponding to the characters 3a, the graduations 3b and the slit 9, so that those portions become luminous. The instrument movement 6 is driven according to a measured value under the condition described above to rotate the pointer plate 8. As a result, the slit 9 as a luminous pointer portion indicates the light-emitting characters 3a and graduations 3b to perform analog display of the information on driving conditions such as vehicle speed.
As illustrated in FIG. 19, the pointer plate 8 is formed slightly larger than the light-transmissible portion 2 so that a peripheral portion 8a of the pointer plate 8 overlaps with a peripheral portion 2a of the light-transmissible portion 2, which prevents the light-transmissible portion 2 from being recognized from a portion a between the dial 1 and the pointer plate 8 when the driver moves his or her eyes from the front of the instrument.
However, a portion b where the dial 1 overlaps with the pointer plate prevents a tip 9a of the slit from sufficiently emitting light by the backlighting to reduce the luminance of the tip 9a of the slit 9, resulting in poor appearance of the apparatus. Therefore, the light-intercepting layer 4 is formed on a surface of the tip also.
However, with the conventional display apparatus described above, a part of the light irradiating the rear face of the pointer plate 8 which reaches a portion corresponding to the slit 9 passes through the slit 9 of the pointer plate 8 so that the quantity of the light is insufficient to cause the luminous pointer portion to be luminous with sufficiently high luminance, which reduces the recognizability and readability of the pointer.
Further, since the light-intercepting layer 4 is formed on the tip 9a of the slit 9 as described above, the length of the slit 9 should be shortened to form the luminous pointer portion. As a result, the tip 9a and the luminous characters 3a become apart from each other as illustrated in FIG. 17, which reduces the recognizability and readability of the pointer.
Further, the length of the slit 9 as the luminous pointer is shortened so that the display apparatus as a whole is looked small under hallucination, which reduces the product value of the apparatus.